The compact city/transit answer to the urban sustainability question
Transit is generally promoted as part of a programme to increase city densities. In Auckland, for example, the plan is to recreate a compact city in order to get people out of cars. A commitment to increasing the capacity of rail-based public transport is intended to support residential densities and justify concentrating public investment in the CBD.
I have addressed some of the issues this raises in earlier blogs. (E.g., Rethink the Link, Five More Reasons, Thin Edge of the Tunnel Wedge, Derailing Auckland)
Source: Tom Tom, 2012; Demographia, 2012
Congestion is additional peak hour travel time compared with free flow travel over the same routes.
(Out of interest, the comparable density figures for Auckland, Hamilton, Wellington and Christchurch are 2,400. 2,200, 1,900, and 2,000 respectively).
The North American evidence: higher density = more congestion?
I undertook simple and multiple regressions in each case to establish how far differences in congestion depend on the physical size of cities, how far on their populations, and how far on residential densities.
Figure 3: Congestion Performance, European cities